Hexapod platforms, which are also known as Gough-Stewart platforms, are used for precisely positioning objects in space. They comprise a fixed base and a top plate that can move with respect to the base. The top plate can move with six degrees of freedom with respect to the base to which is fixed an object the position and orientation configuration of which is to be controlled. This type of platform has numerous applications. Such platforms are, for example, found in the positioning of mechanical workpieces intended to be machined, for the positioning of parabolic antennas or telescopes, for flight simulators, or alternatively, for carrying out tests on how equipment behaves.
A hexapod platform generally comprises six legs of adjustable length connecting the moving top plate to the base. The legs are connected in pairs to the moving top plate and to the base. The pairs alternate so that the two legs of one and the same pair associated with the moving top plate belong to two different pairs associated with the base. In known hexapod platforms, each leg comprises a linear jack articulated at each of its ends to the base and to the moving top plate by means of a ball joint with three degrees of freedom in rotation. Coordinated adjustment of the length of each the six legs allows the moving top plate to be moved with six degrees of freedom.
During movements of the moving top plate, the jacks are all caused to rotate about the ball joints that connect them to the base. The jacks may be hydraulic or electric jacks. They are generally somewhat heavyweight and carry their own on-board drive system. The moving of the jacks accounts for a significant proportion of the overall inertia of the platform. This inertia is to the detriment of very fast movements of this platform.